put this before \begin{document}:
\makeatletter
\long\def\sf@@@subfloat#1[#2][#3]#4{%
\...@ifundefined{fbsc@max}{}%
{...@readaux{\let\fbsuboheight\relax}}%
\...@tempcnta=\@ne
\...@minipage
\...@tempcnta=\z@
\else\ifdim \lastskip=\z@ \else
\...@tempcnta=\tw@
\fi\fi
\ifmaincaptiontop
\...@top=\sf@nearskip
\...@bottom=\sf@farskip
\else
\...@top=\sf@farskip
\...@bottom=\sf@nearskip
\fi
\leavevmode
\setb...@tempboxa \hbox{\beginL#4\endL}%
\...@tempdima=\wd\@tempboxa
\...@ifundefined{fbsc@max}{}%
{\global\advance\xhsize-\...@tempboxa
\di...@=\ht\@tempboxa
\advance\di...@\dp\@tempboxa
\ifdim\dimen@>\f...@max
\global\f...@max\dimen@
\fi}%
\vtop\bgroup
\vbox\bgroup
\ifca...@tempcnta
\...@minipagefalse
\or
\vskip...@top
\or
\ifdim \lastskip=\z@ \else
\...@tempskipb\sf@top\rel...@xaddvskip
\fi
\fi
\...@ifpositiontop{%
\ifx \...@empty#3\relax \else
\...@subcaption{#1}{#2}{#3}%
\vskip...@capskip
\vskip...@captopadj
\fi\egroup
\hrule width0pt height0pt depth0pt
\b...@tempboxa
}{%
\...@ifundefined{fbsc@max}%
{\b...@tempboxa}%
{\ifx\FBsuboheight\relax
\b...@tempboxa
\else
\vbox to \fbsuboheight{\fbafil\b...@tempboxa\fbbfil}%
\fi}%
\egroup
\ifx \...@empty#3\relax \else
\vskip...@capskip
\hrule width0pt height0pt depth0pt
\...@subcaption{#1}{#2}{#3}%
\fi
}%
\vskip...@bottom
\egroup
\...@ifundefined{fbsc@max}{}%
{\addtocounter{FRobj}{-1}%
\ifnu...@frobj=0\else
\subfloatrowsep
\fi}%
\ifmaincaptiontop\else
\global\advan...@nameuse{c@\...@captype}\m@ne
\fi
\endgroup\ignorespaces}
\makeatother
--
Best wishes,
Vafa Khalighi
--------------------------------------------------
Subscriptions, Archive, and List information, etc.:
http://tug.org/mailman/listinfo/xetex
